By KATIE ZEZIMA

Published: November 25, 2006

Gov. Mitt Romney filed a lawsuit Friday asking the state's highest court to order the legislature to vote on a constitutional amendment banning same-sex marriage or to place it on the 2008 ballot if lawmakers do not take up the provision.

The legislature voted 109 to 87 on Nov. 9 to recess a constitutional convention before the measure was taken up, which appeared to kill it. The convention was recessed until Jan. 2, the last day of the legislative session.

More than 170,000 people have signed a petition asking the legislature to amend the state's Constitution to prohibit same-sex marriage. Massachusetts is the only state that permits it.

Mr. Romney, a Republican who did not seek re-election but is considering running for president, announced plans to file the lawsuit at a rally of same-sex marriage opponents on Sunday. The next day he sent a letter to the 109 lawmakers who had voted to recess, saying they were ''frustrating the democratic process and subverting the plain meaning of the Constitution'' by refusing to vote.

The lawsuit, filed by Mr. Romney, acting as a private citizen, and 10 other opponents of same-sex marriage, said the legislature had a ''legal duty to act'' on citizen petitions but had relied on procedural devices to ''avoid a vote and evade its constitutional duties.'' The legislature recessed before voting on the measure two other times this session.

The suit named the Senate president, Robert E. Travaglini, saying he had ''failed to carry out his ministerial duty to require final action'' on the petition. A spokeswoman for Mr. Travaglini, a Democrat, could not be reached for comment.

The suit asks the Supreme Judicial Court to ''step into the constitutional breach'' and direct Secretary of State William F. Galvin, also named in the suit, to place the amendment on the 2008 ballot if the legislature does not act.

Fifty of 200 legislators must vote in favor of the constitutional amendment in this session and in the next one for it to appear as a referendum on the 2008 ballot. Both sides have said the amendment has enough support to advance to the next session.

In a statement, Kris Mineau, the president of the Massachusetts Family Institute, which circulated petitions for the amendment, applauded the lawsuit. Mr. Mineau said that the recess was a ''deliberate effort by those in the legislature to kill the marriage amendment'' and that the legislature had failed to ''afford the citizens a fair up or down vote.''

Gary Buseck, legal director for Gay and Lesbian Advocates and Defenders, which won the lawsuit that led to the legalization of same-sex marriage before the same court, called the lawsuit frivolous.

''I can't see any way in which this lawsuit has any merit whatsoever,'' Mr. Buseck said. ''The bottom line is, the legislature acted in accordance with its rules and the Constitution and did the right thing to protect the now-declared constitutional rights of same-sex couples to marry. There's no getting around that.''

Lawrence M. Friedman, a specialist on Massachusetts constitutional law at the New England School of Law, said the court must decide if the State Constitution requires the legislature to vote. Professor Friedman signed a brief supporting same-sex marriage in 2003 but has not been involved in the issue since then.

''This case is not about same-sex marriage,'' he said. ''This is a case, first, about what the legislature is required to do, and second, if there is anything the court can do about it.

''It's not at all clear to me how this is something the court can remedy. It doesn't seem likely to me the court will order the legislature to take a vote or subvert constitutional procedures and just put it on the ballot.''